Issues of beam intensity measurements under continuous 1 MW operation at J-PARC RCS

Hayashi, Naoki  ; Hatakeyama, Shuichiro; Yoshimoto, Masahiro  

The J-PARC Rapid-Cycling Synchrotron (RCS) is an 1-MW high intensity proton accelerator and its performance has been improved step-by-step. Beam intensity diagnostics is an important device and RCS is equipped two instruments based on different principles, namely DCCT (DC Current Transformer) and SCT (Slow-CT). RCS already achieved 1-MW equivalent operation under very low repetition like single shot. Both basic monitors, DCCT and SCT, did not show any problem. However, SCT showed strange behavior in July 2018 under short-term but continuous 25 Hz 1-MW operation. On the other hand, DCCTalso showed output signal saturation with 1.2-MW equivalent single shot. But, SCT worked properly with this conditions. These problems have to be solved for future continuous 1-MW and higher operation. On this presentation, we will present detailed 700 kW operational data and reproduced data obtained by test-pulse particularly for SCT. We will also try to explain these phenomena by circuit simulation and discuss about how to measure these issues.